Citrus greening found in South Carolina

Peter Kent, Clemson University | Apr 14, 2009

A plant disease that presents a serious threat to the U.S. citrus industry has been located in South Carolina. Federal and state plant-health officials have confirmed the presence of citrus greening (CG).

An infected tree produces fruit that is bitter and unmarketable. Officials are establishing a quarantine to prohibit the movement of citrus plants and other hosts from the area. This is the first confirmation of CG in South Carolina.

The disease was found in a leaf sample from a residential property in Charleston (Charleston County). South Carolina Department of Plant Industry officials plan to remove the infected tree and, in coordination with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS), have begun planning next actions. Surveillance teams will take additional samples for testing, survey the area around the site and gather data on the tree’s history, if possible. Outreach and education to nurseries, plant dealers and citrus hobbyists will be conducted in the near future as well.

Citrus greening, also known as Huanglongbing or HLB, is caused by the bacterial pathogen Candidatus Liberibacter asiaticus. Other than tree removal, there is no effective control once a tree is infected and there is no known cure for the disease.

Citrus greening reduces the quantity and quality of citrus fruits, eventually rendering infected trees useless. In areas of the world affected by citrus greening the average productive lifespan of citrus trees has dropped from 50 or more years to 15 or less. Citrus trees in orchards usually decline within 3 to 5 years after becoming infected and require removal and replanting.

The disease-causing bacteria are spread by the Asian citrus psyllid (ACP). While officials found the insect in the Charleston area in 2008 and performed molecular analysis on the specimen collected, they did not detect any symptoms of citrus greening bacteria.

Last year, Asian citrus psyllids were not detected on this specific tree during surveys conducted by APHIS and the state, but were detected less than a mile away. The insect also was found on citrus in Beaufort and Colleton counties. The presence of psyllids in the three counties led to federal and state quarantines of Beaufort, Charleston and Colleton counties.

With the confirmation of citrus greening in Charleston, federal plant officials are seeking to establish a citrus greening quarantine in Charleston County. South Carolina officials have indicated that the state intends to take action to establish a parallel quarantine. The dual action makes it possible for federal regulators to hold the quarantine for CG only in those counties in South Carolina in which the disease is present.

Citrus greening has been in Asia and Africa for decades. It was detected in Brazil in 2004. APHIS confirmed the disease in Florida in 2005 and Louisiana in 2008. The 2005-2006 Florida citrus crop had an on-tree value of $1.04 billion.